A dual grid strategy for subgrid reaction-rate closure using linear eddy mixing model for large-eddy simulation of turbulent combustion*

The reaction-rate closure for large-eddy simulation (LES) of turbulent combustion, referred to as RRLES, employs the linear eddy mixing (LEM) model at the subgrid for closure of the filtered reaction-rate term. The originally proposed RRLES strategy used a multilevel adaptive mesh refinement (AMR) framework to address some of the limitations of the well-established LEMLES strategy. In comparison to LEMLES, where the subgrid scalar field evolved using the LEM model is coupled with resolved level through a Lagrangian transport, RRLES only employs LEM to model the reaction-rate term. To enable the application of RRLES to complex geometries, a single grid-based strategy was developed. However, the multilevel technique tends to be more accurate for capturing the subgrid turbulence-chemistry interactions. In the present study, a local dual grid-based strategy is developed, which can potentially be used with different grid topologies, without the need for an AMR. The proposed approach is evaluated by simulating freely propagating methane/air turbulent premixed flames at different operating conditions. The effectiveness of the approach is assessed by comparing features of flame-turbulence interactions obtained from the single grid-based RRLES and reference direct numerical simulations.